Electrode structure and all solid secondary battery including the same

Abstract

An electrode structure comprising an anode layer, a cathode layer, and a solid electrolyte layer disposed between the anode layer and the cathode layer, wherein the anode layer comprises an anode current collector and an anode active material layer disposed on at least one surface of the anode current collector, and the cathode layer comprises a cathode current collector and a cathode active material layer disposed on at least one surface of the cathode current collector, and wherein an insulating layer having a storage elastic modulus (E') of greater than 4.0 GPa is included on both sides that integrally surrounds the anode layer, the cathode layer, and the solid electrolyte layer. An all-solid-state secondary battery comprising the same is disclosed.

Description

Technology Field

[0001] The present invention relates to an electrode structure and an all-solid-state secondary battery including the same. Background Technology

[0002] Recently, driven by industrial demands, the development of batteries with high energy density and safety is actively underway. For example, lithium-ion batteries are being commercialized not only in the fields of information and communication devices but also in the automotive sector. In the automotive sector, safety is considered particularly important because it is directly related to human life.

[0003] Currently commercially available lithium-ion batteries use electrolytes containing flammable organic solvents, so there is a possibility of overheating and fire in the event of a short circuit. In response to this, all-solid-state secondary batteries using solid electrolytes instead of liquid electrolytes are being proposed.

[0004] By not using flammable organic solvents, all-solid-state rechargeable batteries can significantly reduce the likelihood of fire or explosion even in the event of a short circuit. Therefore, these all-solid-state rechargeable batteries can offer significantly higher safety compared to lithium-ion batteries that use liquid electrolytes. Prior art literature

[65535] Korean Patent Publication No. 10-2018-0128573, International Patent Publication No. 2006-046534 The problem to be solved

[0005] One aspect is to provide an electrode structure with a new structure.

[0006] Another aspect is to provide an all-solid-state secondary battery comprising the electrode structure described above. means of solving the problem

[0007] Depending on one aspect

[0008] An electrode structure comprising an anode layer, a cathode layer, and a solid electrolyte layer disposed between the cathode layers,

[0009] The above positive layer comprises a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, and

[0010] The above cathode layer comprises a cathode current collector and a cathode active material layer disposed on at least one surface of the cathode current collector, and

[0011] An electrode structure is provided comprising an insulating layer having a storage modulus (E') of greater than 4.0 GPa on both sides integrally surrounding the anode layer, the cathode layer, and the solid electrolyte layer.

[0012] The above insulating layer may have a loss tangent (tanδ) of less than 0.5.

[0013] The above insulating layer is 1 x 10 6 It can have a resistivity of ohm / cm or more.

[0014] The above insulating layer may be at least one layer.

[0015] The above insulating layer may include a polymer, or a composite of a polymer and an inorganic material.

[0016] The above polymer may include fluorine-based polymers, cellulose-based polymers, epoxy-based resins, or combinations thereof.

[0017] In the composite of the polymer and inorganic material, the volume ratio of the polymer may be 50 volume% or more based on 100 volume% of the total composition for forming the composite.

[0018] The above-mentioned inorganic material may include metal oxides, metal hydroxides, or a combination thereof.

[0019] The composite density of the above positive active material layer may be 3.0 g / cc or higher.

[0020] The above positive active material layer may include a sulfide-based solid electrolyte.

[0021] The above-mentioned negative electrode active material layer may include one or more selected from carbon-based negative electrode active materials and metal or metal-metal negative electrode active materials.

[0022] The above carbon-based negative electrode active material may include one or more selected from amorphous carbon and crystalline carbon.

[0023] The above metal or metalloid cathode active material may include one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn).

[0024] The above solid electrolyte layer may not have a margin at both ends in the width direction, or may have a margin of 2% or less of the width of the above solid electrolyte layer.

[0025] The above solid electrolyte layer may include a sulfide-based solid electrolyte represented by the following chemical formula 1:

[0026] [Chemical Formula 1]

[0027] Li + 12-n-x A n+ X 2- 6-x Y - x

[0028] In the above formula, A can be P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, or Ta, and

[0029] X is S, Se, or Te, and Y can be Cl, Br, I, F, CN, OCN, SCN, or N3, and 1 < n < 5, 0 < n < 2.

[0030] The above solid electrolyte layer may have a peel strength of 0.2 gf / mm or more with respect to the anode layer or the cathode layer.

[0031] The above electrode structure may be in the form of a jelly roll or a stack.

[0032] The above electrode structure may not crack when compressed to 20-30% of its thickness in the thickness direction.

[0033] Depending on other aspects of work

[0034] An all-solid-state secondary battery including the aforementioned electrode structure is provided. Effects of the invention

[0035] An electrode structure according to one embodiment comprises an anode layer, a cathode layer, and a solid electrolyte layer disposed between the anode layer and the cathode layer, and includes an insulating layer having a storage modulus (E') of greater than 4.0 GPa on both sides that integrally surrounds the anode layer, the cathode layer, and the solid electrolyte layer.

[0036] The above electrode structure can provide an all-solid-state secondary battery with improved lifespan characteristics while minimizing initial capacity degradation by suppressing short circuits through the insulating layer even when the margin of the width of the solid electrolyte layer is very small or non-existent. Brief explanation of the drawing

[0037] FIG. 1 is a schematic cross-sectional view of an electrode structure according to one embodiment. FIG. 2 is a schematic cross-sectional view showing a stacked electrode structure according to one embodiment and partially showing the interior thereof. FIG. 3 is a schematic diagram of an all-solid-state secondary battery according to one embodiment. Figure 4 is a graph showing the lifespan characteristics of all-solid-state secondary batteries produced by Examples 1 to 3 and Comparisons 1 to 2. Specific details for implementing the invention

[0038] Hereinafter, an electrode structure according to one embodiment of the present invention and an all-solid-state secondary battery including the same will be described in detail with reference to the attached drawings. The following is presented as an example and is not intended to limit the present invention, and the present invention is defined only by the scope of the claims set forth below.

[0039] In this specification, expressions such as "at least one," "one or more," or "one or more" preceding components are to supplement the list of all components and do not mean that they are to supplement the individual components described above. In this specification, the term "combination" includes mixtures, alloys, reaction products, etc., unless specifically stated otherwise.

[0040] In this specification, the term "includes" means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0041] In this specification, terms such as "first," "second," etc., are used to distinguish one element from another without indicating order, quantity, or importance. Unless otherwise indicated in this specification or clearly contradicted by the context, they should be interpreted to include both singular and plural forms. "Or" means "and / or" unless otherwise specified.

[0042] Throughout this specification, terms such as “one embodiment,” “an embodiment,” etc., mean that specific elements described in relation to an embodiment are included in at least one embodiment described herein and may or may not be present in other embodiments. Furthermore, it should be understood that the described elements may be combined in any appropriate manner in various embodiments.

[0043] Unless otherwise defined, technical and scientific terms used herein have the same meaning as generally understood by those skilled in the art to which this application pertains. All cited patents, patent applications, and other references are incorporated herein by reference in their entirety. However, in the event that terms in this specification contradict or conflict with terms in the incorporated reference, terms from this specification shall prevail over conflicting terms in the incorporated reference. Although specific embodiments and embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are not currently anticipated or cannot be anticipated may arise to the applicant or those skilled in the art. Accordingly, the appended claims and subject to amendment are intended to include all such alternatives, variations, improvements, and substantial equivalents.

[0045] All-solid-state secondary batteries are advantageous in terms of stability, but because the electrolyte is solid, they have lower flexibility and processability compared to lithium-ion batteries. For this reason, it is difficult to secure a margin of width between the electrode plates and the electrolyte membrane in an electrode structure composed of a positive plate, a negative plate, and an electrolyte membrane. In addition, burrs or cracks may occur on the outermost edge surfaces of the electrode plates and the electrolyte membrane. In such cases, a short circuit may occur inside the all-solid-state secondary battery, which may degrade capacity and lifespan characteristics. The inventor of the present invention aims to solve the problem of degraded capacity and lifespan characteristics by designing a new layer on the side of the electrode structure.

[0046] The electrode structure and all-solid-state secondary battery according to exemplary embodiments are described in more detail below.

[0047] [Electrode structure]

[0048] An electrode structure according to one embodiment is an electrode structure comprising an anode layer, a cathode layer, and a solid electrolyte layer disposed between the anode layer and the cathode layer, wherein the anode layer comprises an anode current collector and an anode active material layer disposed on at least one surface of the anode current collector, the cathode layer comprises a cathode current collector and a cathode active material layer disposed on at least one surface of the cathode current collector, and the solid electrolyte layer does not have a margin at both ends in the width direction or has a margin of 2% or less of the width of the solid electrolyte layer, and may include an insulating layer having a storage modulus (E') greater than 4.0 GPa on both sides that integrally surround the anode layer, the cathode layer, and the solid electrolyte layer.

[0049] The electrode structure comprises insulating layers on both sides that integrally surround the anode layer, the cathode layer, and the solid electrolyte layer. The insulating layer has a storage modulus (E') greater than 4.0 GPa. Generally, the storage modulus (E') of the insulating layer is high when the storage modulus (E') of the solid electrolyte layer is 1.3 to 4.0. Therefore, the electrode structure does not undergo deformation due to pressure during battery manufacturing, and as a result, short circuits are prevented. This allows for the prevention of short circuits even when the solid electrolyte layer has no clearance at both ends in the width direction, or when the clearance is very small, such as 2% or less of the width of the solid electrolyte layer.

[0050] FIG. 1 is a schematic cross-sectional view of an electrode structure according to one embodiment. FIG. 2 is a schematic cross-sectional view showing a stacked electrode structure according to one embodiment and a portion of the interior thereof.

[0051] Referring to FIG. 1, the electrode structure (10) has an anode layer (1), a solid electrolyte layer (2), and a cathode layer (3) arranged in order, and an insulating layer (4) is arranged on both sides that integrally surround the anode layer (1), the solid electrolyte layer (2), and the cathode layer (3). The solid electrolyte layer (2) has a w margin at both ends in the width direction. For example, the w margin may be 0.5 mm or less.

[0052] Referring to FIG. 2, the electrode structure (30) is a stack-type bi-cell structure. The electrode structure (30) has an anode layer (26, 26') with an anode active material layer (22, 22') disposed on the upper and lower surfaces of an anode current collector (21), a solid electrolyte layer (23, 23') disposed on one side of the anode layer (26, 26'), and a cathode layer (27, 27') composed of a cathode active material layer (25, 25') and a cathode current collector (24, 24') disposed on one side of the solid electrolyte layer (23, 23'). Insulating layers (28, 28') are disposed on both sides of the anode layer (26, 26'), the solid electrolyte layer (23, 23'), and the cathode layer (27, 27'), respectively.

[0053] The electrode structure (30) is exemplified as a stacked form, but may be in a jelly roll form or a stacked form.

[0054] When the electrode structure (30) is compressed to 20-30% of its thickness in the thickness direction, cracks may not occur in the electrode structure (30).

[0055] [Insulation layer]

[0056] The insulating layer (28, 28') may have a storage modulus (E') greater than 4.0 GPa. The electrode structure (10, 30) including the insulating layer (28, 28') having such a storage modulus (E') does not undergo deformation under pressure when manufacturing a battery in a jelly roll or stack form, and short circuits are prevented.

[0057] The insulating layer (28, 28') may have a loss tangent (tanδ) of less than 0.5. The loss tangent (tanδ) is the ratio of the storage non-elastic modulus (E") to the storage elastic modulus (E'), i.e., E" / E'. The loss tangent (tanδ) is related to the restoring force. The restoring force is the force that recovers to its original state after being deformed by pressure during battery manufacturing, and it reduces the probability of a short circuit occurring during the charging and discharging of the battery. Generally, when the loss tangent (tanδ) of the solid electrolyte layer is 0.05 to 0.15, the loss tangent (tanδ) of the insulating layer (28, 28') is low. Therefore, the electrode structure (10, 30) exerts a restoring force during battery manufacturing, so deformation does not occur due to pressure, and as a result, a short circuit is prevented.

[0058] The storage modulus (E') and storage inelastic modulus (E") of the insulating layer (28, 28') can be obtained using dynamic mechanical analysis (DMA). For example, the storage modulus (E') and storage inelastic modulus (E") can be derived by applying an external force in the form of a sinusoidal wave with a frequency of 1 Hz to a sample of size 10 mm x 5 mm and measuring the displacement and phase of the sample deformed according to the force.

[0059] The insulating layer (28, 28') is 1 x 10 6 It can have a resistivity of ohm / cm or greater. The insulating layer (28, 28') is electrically insulated so that a short circuit inside the electrode assembly (10, 30) can be suppressed.

[0060] The insulating layer (28, 28') may be at least one layer. For example, the insulating layer (28, 28') may be two layers or three or more layers. The number of layers of the insulating layer (28, 28') can be adjusted within a range that satisfies the storage elastic modulus (E'), the storage inelastic modulus (E"), and the loss tangent (tanδ).

[0061] The insulating layer (28, 28') may include a polymer, or a composite of a polymer and an inorganic material. Examples of the polymer may include a fluorine-based polymer, a cellulose-based polymer, an epoxy resin, or a combination thereof.

[0062] Examples of the above-mentioned fluorine-based polymers may be homopolymers of vinylidene fluoride monomers, or copolymers of vinylidene fluoride monomers and one or more fluorine-containing monomers selected from tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, fluorovinyl, and perfluoroalkyl vinyl ethers. Specifically, the vinylidene-based monomers may be vinylidene fluoride homopolymers, vinylidene fluoride-hexafluoropropylene copolymers, vinylidene fluoride-chlorotrifluoroethylene copolymers, etc.

[0063] Optionally, the fluorinated polymer may be a copolymer of a monomer containing a polar functional group and a vinylidene fluoride monomer, or may further comprise a copolymer of a monomer containing a polar functional group, a vinylidene fluoride monomer, and other fluorinated monomers described above. For example, the vinylidene fluoride polymer containing a polar functional group may be a copolymer of a monomer containing a polar functional group and vinylidene fluoride, a copolymer of a monomer containing a polar functional group and vinylidene fluoride and hexafluoropropylene, a copolymer of a monomer containing a polar functional group and vinylidene fluoride and chlorotrifluoroethylene copolymer, etc. The polar functional group may be one or more selected from carboxylic acid groups, sulfonic acid groups, phosphate groups, hydroxyl groups, and salts thereof, but is not necessarily limited to these, and any that can be used as a polar functional group in the art is acceptable. The introduction of polar functional groups into the above-mentioned fluorine-based polymer can be carried out by polymerizing monomers comprising carboxylic acid groups, sulfonic acid groups, phosphate groups, hydroxyl groups, and salts thereof. Monocarboxylic acids include monocarboxylic acids and their derivatives, dicarboxylic acids, and their derivatives. Examples of monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid. Examples of monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, and β-diaminoacrylic acid. Examples of dicarboxylic acids include maleic acid, fumaric acid, and itaconic acid. Examples of dicarboxylic acid derivatives include maleate salts such as methylallyl maleate, diphenyl maleate, nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, and fluoroalkyl maleate, such as methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, and fluoromaleic acid. Additionally, acid anhydrides that generate a carboxyl group upon hydrolysis may also be used. Examples of acid anhydrides of dicarboxylic acids include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride.In addition, monoesters and diesters of α,β-ethylenically unsaturated polycarboxylic acids such as monoethyl maleate, diethyl maleate, monobutyl maleate, dibutyl maleate, monoethyl fumarate, diethyl fumarate, monobutyl fumarate, dibutyl fumarate, monocyclohexyl fumarate, dicyclohexyl fumarate, monoethyl itaconate, diethyl itaconate, monobutyl itaconate, and dibutyl itaconate may be used. Monomers having a sulfonic acid group include vinylsulfonic acid, methylvinylsulfonic acid, (meth)allylsulfonic acid, styrenesulfonic acid, (meth)acrylate-2-sulfonate ethyl, 2-acrylamide-2-methylpropanesulfonic acid, 3-allyloxy-2-hydroxypropanesulfonic acid, etc. Examples of monomers having a phosphate group include 2-(meth)acryloyloxyethyl phosphate, methyl-2-(meth)acryloyloxyethyl phosphate, and ethyl-(meth)acryloyloxyethyl phosphate. Examples of monomers having a hydroxyl group include ethylenically unsaturated alcohols such as (meth)allyl alcohol, 3-buten-1-ol, and 5-hexene-1-ol; alkanol esters of ethylenically unsaturated carboxylic acids such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, di2-hydroxyethyl maleate, di4-hydroxybutyl maleate, and di2-hydroxypropyl itaconate; general formula CH2=CR. 1- COO-(C n H 2n O) mEsters of polyalkylene glycols and (meth)acrylic acids represented by -H (m is an integer from 2 to 9, n is an integer from 2 to 4, and R1 represents hydrogen or a methyl group); mono(meth)acrylic acid esters of dihydroxyesters of dicarboxylic acids such as 2-hydroxyethyl-2'-(meth)acryloyloxyphthalate and 2-hydroxyethyl-2'-(meth)acryloyloxysuccinate; vinyl ethers such as 2-hydroxyethyl vinyl ether and 2-hydroxypropyl vinyl ether; Mono(meth)allyl ethers of alkylene glycols such as (meth)allyl-2-hydroxyethyl ether, (meth)allyl-2-hydroxypropyl ether, (meth)allyl-3-hydroxypropyl ether, (meth)allyl-2-hydroxybutyl ether, (meth)allyl-3-hydroxybutyl ether, (meth)allyl-4-hydroxybutyl ether, (meth)allyl-6-hydroxyhexyl ether; polyoxyalkylene glycol (meth)monoallyl ethers such as diethylene glycol mono(meth)allyl ether, dipropylene glycol mono(meth)allyl ether; Examples include mono(meth)allyl ethers of (poly)alkylene glycols with halogen and hydroxyl substituents, such as glycerin mono(meth)allyl ether, (meth)allyl-2-chloro-3-hydroxypropyl ether, (meth)allyl-2-hydroxy-3-chloropropyl ether; mono(meth)allyl ethers of polyphenols such as eugenol and isoeugenol and their halogen substituents; and (meth)allylthioethers of alkylene glycols such as (meth)allyl-2-hydroxyethylthioether and (meth)allyl-2-hydroxypropylthioether. The above-mentioned fluorine-based polymer can provide a battery with improved energy density and lifespan characteristics by improving adhesion and flexibility with the electrode plate.

[0064] Examples of the above-mentioned cellulose-based polymers may include one or more selected from cellulose, methyl cellulose, ethyl cellulose, butyl cellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate. There are no restrictions on the form of the above-mentioned cellulose-based polymer, but it may be, for example, in the form of nanofibers. The above-mentioned cellulose-based polymer has excellent mechanical strength and optical transparency. Therefore, a battery containing the cellulose-based polymer as an insulating layer (28, 28') can have excellent lifespan characteristics and stability.

[0065] The above epoxy resin may be one or more selected from cresol novolak epoxy resin, bisphenol A type epoxy resin, bisphenol A type novolak epoxy resin, phenol novolak epoxy resin, tetrafunctional epoxy resin, biphenyl type epoxy resin, triphenol methane type epoxy resin, alkyl modified triphenol methane epoxy resin, naphthalene type epoxy resin, dicyclopentadiene type epoxy resin, dicyclopentadiene modified phenol type epoxy resin, urethane modified epoxy resin, and combinations thereof, but is not limited thereto. The above epoxy resin is excellent in mechanical properties and electrical insulation properties.

[0066] In the above polymer and inorganic material composite, the volume ratio of the polymer may be 50 volume% or more based on 100 volume% of the total composition for forming the composite. Within the above range of the polymer volume ratio, physical properties such as the storage modulus (E') and storage specific modulus (E") of the insulating layer (28, 28') can be enhanced. Additionally, as the weight ratio of the inorganic material in the above polymer and inorganic material composite increases, the strength of the polymer and inorganic material composite and the storage modulus (E') may increase, but there is also a possibility that the storage specific modulus (E") may increase. Therefore, the weight ratio of the polymer to the inorganic material in the above polymer and inorganic material composite may be 1:1 to 1:5. Within the above range of the polymer to inorganic material weight ratio, physical properties such as the storage modulus (E') and storage specific modulus (E") of the insulating layer (28, 28') can be enhanced.

[0067] The above-mentioned inorganic material may include metal oxides, metal hydroxides, or combinations thereof. Examples of the above-mentioned inorganic material may include Al2O3, Al(OH)3, etc., but are not limited thereto; any inorganic material usable in the field of all-solid-state secondary batteries may be used.

[0068] [Bipolar]

[0069] The positive layer (26, 26') includes a positive current collector (21) and a positive active material layer (22, 22') disposed on at least one surface of the positive current collector (21).

[0070] The positive active material layer (22, 22') includes, for example, a positive active material and a solid electrolyte. The solid electrolyte included in the positive layer (26, 26') is similar to or different from the solid electrolyte included in the solid electrolyte layer (23, 23'). For example, the solid electrolyte may include a sulfide-based solid electrolyte. For details regarding the solid electrolyte, refer to the solid electrolyte layer (23, 23').

[0071] The cathode active material is a cathode active material capable of reversibly absorbing and desorbing lithium ions. The cathode active material may be, for example, lithium transition metal oxides such as lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganate, and lithium iron phosphate, nickel sulfide, copper sulfide, lithium sulfide, iron oxide, or vanadium oxide, but is not necessarily limited to these; any material used as a cathode active material in the relevant technical field is acceptable. The cathode active material may be a single material or a mixture of two or more materials.

[0072] Lithium transition metal oxides are, for example, Li a A 1-b B' b D'2(wherein 0.90 ≤ a ≤ 1, and 0 ≤ b ≤ 0.5); Li a E 1-b B' b O 2-c D' c (In the above formula, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B' b O 4-c D' c (In the above equation, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B' c D' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B' c O 2-α F' α(In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Co b B' c O 2-α F'2(wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B' c D' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B' c O 2-α F' α (In the above equation, 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B' c O 2-α F'2(wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G d O2(wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d G e O2(wherein 0.90 ≤ a ≤ 1, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG bO2(in the above equation, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a CoG b O2(in the above equation, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a MnG b O2(in the above equation, 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4(wherein 0.90 ≤ a ≤ 1, 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiI'O2; LiNiVO4; Li (3-f) J2(PO4)3(0 ≤ f ≤ 2); Li (3-f)Fe2(PO4)3(0 ≤ f ≤ 2); a compound represented by any one of the chemical formulas of LiFePO4. In such a compound, A is Ni, Co, Mn, or a combination thereof; B' is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D' is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F' is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I' is Cr, V, Fe, Sc, Y, or a combination thereof; and J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof. A compound having a coating layer added to the surface of such a compound may also be used, and a mixture of the above-described compound and a compound having a coating layer added may also be used. The coating layer applied to the surface of such a compound comprises, for example, a coating element compound of an oxide, hydroxide, oxyhydroxide, oxycarbonate, or hydroxycarbonate of a coating element. The compound forming this coating layer is amorphous or crystalline. The coating elements included in the coating layer are Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The method for forming the coating layer is selected within a range that does not adversely affect the physical properties of the cathode active material. The coating method is, for example, spray coating or immersion. Since specific coating methods are well understood by those skilled in the art, a detailed explanation will be omitted.

[0073] The cathode active material includes, for example, a lithium salt of a transition metal oxide having a layered rock salt type structure among the lithium transition metal oxides described above. The "layered rock salt type structure" is, for example, a cubic rock salt type structure. <111> It is a structure in which oxygen and metal atomic layers are alternately and regularly arranged in a specific direction, thereby forming a two-dimensional plane for each layer. The "cubic rock salt type structure" represents a sodium chloride (NaCl type) structure, which is a type of crystal structure; specifically, it exhibits a structure in which the face-centered cubic lattices (fcc) formed by cations and anions, respectively, are offset from each other by half the ridge of the unit lattice. Lithium transition metal oxides having such a layered rock salt type structure, for example, LiNi x Co y Al z O2(NCA) or LiNi x Co y Mn z It is a ternary lithium transition metal oxide such as O2(NCM) (0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1). When the cathode active material includes a ternary lithium transition metal oxide having a layered rock salt structure, the energy density and thermal stability of the all-solid-state secondary battery are further improved.

[0074] The positive electrode active material may be covered by a coating layer as described above. The coating layer may be any material known as a coating layer for the positive electrode active material of an all-solid-state secondary battery. For example, the coating layer is Li2O-ZrO2 (LZO), etc.

[0075] When the cathode active material is a ternary lithium transition metal oxide, such as NCA or NCM, containing nickel (Ni), it is possible to increase the capacity density of the all-solid-state secondary battery and reduce metal leaching from the cathode active material during charging. Consequently, the cycle characteristics of the all-solid-state secondary battery during charging are improved.

[0076] The shape of the positive active material is, for example, a particle shape such as a sphere, an elliptical sphere, etc. The particle size of the positive active material is not particularly limited and is within a range applicable to the positive active material of a conventional all-solid-state secondary battery. The content of the positive active material of the positive layer (26, 26') is also not particularly limited and is within a range applicable to the positive layer of a conventional all-solid-state secondary battery.

[0077] The solid electrolyte included in the positive electrode active material layer (22, 22') may have a smaller D50 average particle size compared to the solid electrolyte included in the solid electrolyte layer (23, 23'). For example, the D50 average particle size of the solid electrolyte included in the positive electrode active material layer (22, 22') may be 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less of the D50 average particle size of the solid electrolyte included in the solid electrolyte layer (23, 23').

[0078] The average particle size of D50 is, for example, the median particle diameter (D50). The median particle diameter (D50) is the particle size corresponding to 50% of the cumulative volume calculated from the particle side having a small particle size in the particle size distribution measured, for example by laser diffraction.

[0079] The positive active material layer (22, 22') may include a binder. The binder may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited to these, and any binder used in the relevant technical field is acceptable.

[0080] The positive active material layer (22, 22') may include a conductive material. The conductive material may be, for example, graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powder, etc., but is not limited to these and any material used as a conductive material in the relevant technical field is possible.

[0081] The positive active material layer (22, 22') may further include additives such as fillers, coating agents, dispersants, and ion conductivity aids in addition to the positive active material, solid electrolyte, binder, and conductive material described above.

[0082] The filler, coating agent, dispersant, ion-conducting auxiliary agent, etc. that may be included in the positive active material layer (22, 22') may be any known material generally used in the electrodes of all-solid-state secondary batteries.

[0083] The composite density of the positive active material layer (22, 22') may be 3.0 g / cc or higher.

[0084] The positive current collector (21) is made of, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof, such as a plate or foil. The positive current collector (21) may be omitted. The thickness of the positive current collector (21) is, for example, 1 µm to 100 µm, 1 µm to 50 µm, 5 µm to 25 µm, or 10 µm to 20 µm.

[0085] [Solid Electrolyte Layer]

[0086] Referring to FIGS. 1 and 2, the solid electrolyte layer (2, 23, 23') includes a solid electrolyte disposed between the anode layer (1, 26, 26') and the cathode layer (3, 27, 27').

[0087] Solid electrolytes are, for example, sulfide-based solid electrolytes. Sulfide-based solid electrolytes are, for example, Li2S-P2S5, Li2S-P2S5-LiX, where X is a halogen element, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n , m, n are positive numbers, Z is one of Ge, Zn, or Ga, Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q , p, q are positive numbers, M is one of P, Si, Ge, B, Al, Ga, In, Li 7-x PS 6-x Cl x , 0*?*x*2, Li 7-x PS 6-x Br x , 0*x*2, and Li 7-x PS 6-x I xIt is one or more selected from , 0*x*2. Sulfide-based solid electrolytes are manufactured by processing starting materials, such as Li2S and P2S5, by methods such as melt quenching or mechanical milling. Additionally, heat treatment may be performed after such processing. The solid electrolyte may be amorphous, crystalline, or a mixture thereof. Furthermore, the solid electrolyte may include sulfur (S), phosphorus (P), and lithium (Li) as at least constituent elements among the sulfide-based solid electrolyte materials described above. For example, the solid electrolyte may be a material containing Li2S-P2S5. When using a sulfide-based solid electrolyte material containing Li2S-P2S5 to form the solid electrolyte, the mixed molar ratio of Li2S and P2S5 is, for example, in the range of Li2S:P2S5 = 50:50 to 90:10.

[0088] Sulfide-based solid electrolytes may include, for example, an argyrodite-type solid electrolyte represented by the following chemical formula 1:

[0089] [Chemical Formula 1]

[0090] Li + 12-n-x A n+ X 2- 6-x Y - x

[0091] In the above formula, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, or Ta; X is S, Se, or Te; Y is Cl, Br, I, F, CN, OCN, SCN, or N3; and 1*n*5, 0*x*2. Sulfide-based solid electrolytes are, for example, Li 7-x PS 6-x Cl x , 0≤x≤2, Li 7-x PS 6-x Br x , 0≤x≤2, and Li 7-x PS6-x I x It may be an argyrodite-type compound containing one or more selected from 0≤x≤2. The sulfide-based solid electrolyte may be an argyrodite-type compound containing one or more selected from, for example, Li6PS5Cl, Li6PS5Br, and Li6PS5I.

[0092] The density of the argyrodite-type solid electrolyte may be 1.5 to 2.0 g / cc. Since the argyrodite-type solid electrolyte has a density of 1.5 g / cc or higher, the internal resistance of the all-solid-state secondary battery is reduced, and penetration of the solid electrolyte layer by Li can be effectively suppressed.

[0093] The solid electrolyte layer (2, 23, 23') may include, for example, a binder. The binder included in the solid electrolyte layer (2, 23, 23') may be, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc., but is not limited to these, and any binder used in the relevant technical field is possible. The binder of the solid electrolyte layer (2, 23, 23') may be the same as or different from the binder included in the positive electrode active material layer (22, 22') and the negative electrode active material layer (25, 25'). The binder may be omitted.

[0094] The binder content included in the solid electrolyte layer (2, 23, 23') is 0 to 10 wt%, 0 to 5 wt%, 0 to 3 wt%, 0 to 1 wt%, 0 to 0.5 wt%, or 0 to 0.1 wt% based on the total weight of the solid electrolyte layer (2, 23, 23').

[0095] The solid electrolyte layer (2, 23, 23') may have a peel strength of 0.2 gf / mm or more with the anode layer (26, 26') or the cathode layer (27, 27').

[0096] [Cathode layer]

[0097] The negative electrode layer (27, 27') includes a negative electrode current collector (24, 24') and a negative electrode active material layer (25, 25') disposed on at least one surface of the negative electrode current collector (24, 24').

[0098] The negative electrode active material layer (25, 25') includes, for example, a negative electrode active material and a binder.

[0099] The negative electrode active material included in the negative electrode active material layer (25, 25') has, for example, a particle form. The average particle size of the negative electrode active material having a particle form is, for example, 4 µm or less, 3 µm or less, 2 µm or less, 1 µm or less, or 900 nm or less. The average particle size of the negative electrode active material having a particle form is, for example, 10 nm to 4 µm or less, 10 nm to 3 µm or less, 10 nm to 2 µm or less, 10 nm to 1 µm or less, or 10 nm to 900 nm or less. By having the negative electrode active material with an average particle size within this range, the reversible absorption and / or desorption of lithium during charging and discharging may be more facilitated. The average particle size of the negative electrode active material is, for example, the median diameter (D50) measured using a laser particle size distribution meter.

[0100] The negative electrode active material included in the negative electrode active material layer (25, 25') comprises, for example, one or more selected from carbon-based negative electrode active materials and metal or metalloid negative electrode active materials.

[0101] The carbon-based cathode active material may include one or more selected from amorphous carbon and crystalline carbon. The carbon-based cathode active material may be, for example, amorphous carbon. Amorphous carbon may be, for example, carbon black (CB), acetylene black (AB), furnace black (FB), Kettjen black (KB), graphene, etc., but is not necessarily limited to these, and any carbon classified as amorphous carbon in the relevant technical field is possible. Amorphous carbon is carbon that does not have crystallinity or has very low crystallinity and is distinguished from crystalline carbon or graphite-based carbon.

[0102] The metal or metalloid cathode active material comprises one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn), but is not necessarily limited to these; any metal cathode active material or metalloid cathode active material that forms an alloy or compound with lithium in the relevant technical field is acceptable. For example, nickel (Ni) is not a metal cathode active material because it does not form an alloy with lithium.

[0103] The negative electrode active material layer (25, 25') may include a type of negative electrode active material among these negative electrode active materials, or may include a mixture of multiple different negative electrode active materials. For example, the negative electrode active material layer (22) may include only amorphous carbon, or one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). Alternatively, the negative electrode active material layer (25, 25') may include a mixture of amorphous carbon and one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). The mixing ratio of a mixture of amorphous carbon and gold, etc., is, for example, 10:1 to 1:2, 5:1 to 1:1, or 4:1 to 2:1 by weight ratio, but is not necessarily limited to these ranges and is selected according to the required characteristics of the all-solid-state secondary battery (1). By having the negative electrode active material have this composition, the lifespan characteristics of the all-solid-state secondary battery (1) are further improved.

[0104] The negative electrode active material included in the negative electrode active material layer (25, 25') comprises a mixture of first particles made of, for example, amorphous carbon and second particles made of a metal or metalloid. The metal or metalloid includes, for example, gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). Alternatively, the metalloid is a semiconductor. The content of the second particles is 8 to 60 weight%, 10 to 50 weight%, 15 to 40 weight%, or 20 to 30 weight% based on the total weight of the mixture. By having the second particles in this range, the life characteristics of, for example, the all-solid-state secondary battery are further improved.

[0105] The binder included in the negative electrode active material layer (25, 25') may be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., but is not necessarily limited to these, and any binder used in the relevant technical field is possible. The binder may be composed of a single binder or a plurality of different binders.

[0106] By including a binder, the negative active material layer (25, 25') is stabilized on the negative current collector (24, 24'). Additionally, cracking of the negative active material layer (25, 25') is suppressed despite volume changes and / or relative position changes of the negative active material layer (25, 25') during the charging and discharging process. For example, if the negative active material layer (25, 25') does not include a binder, it is possible for the negative active material layer (25, 25') to be easily separated from the negative current collector (24, 24'). As the negative active material layer (25, 25') separates from the negative current collector (24, 24'), the negative current collector (24, 24') comes into contact with the solid electrolyte layer (23, 23') at the exposed portion, thereby increasing the likelihood of a short circuit. The negative active material layer (25, 25') is manufactured, for example, by applying a slurry in which the material constituting the negative active material layer (25, 25') is dispersed onto the negative current collector (24, 24') and drying it. By including a binder in the negative active material layer (25, 25'), stable dispersion of the negative active material in the slurry is possible. For example, when applying the slurry onto the negative current collector (24, 24') using a screen printing method, it is possible to suppress clogging of the screen (for example, clogging caused by aggregates of the negative active material).

[0107] The negative electrode active material layer (25, 25') may further include additives used in conventional all-solid-state secondary batteries, such as fillers, coating agents, dispersants, ion-conducting aids, etc.

[0108] The thickness of the negative electrode active material layer (25, 25') is, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, or 5% or less of the thickness of the positive electrode active material layer (22, 22'). The thickness of the negative electrode active material layer (25, 25') is, for example, 1 µm to 20 µm, 2 µm to 10 µm, or 3 µm to 7 µm. If the thickness of the negative electrode active material layer (25, 25') is excessively thin, lithium dendrites formed between the negative electrode active material layer (25, 25') and the negative electrode current collector (24, 24') cause the negative electrode active material layer (25, 25') to collapse, making it difficult to improve the lifespan characteristics of the all-solid-state secondary battery. If the thickness of the negative electrode active material layer (25, 25') increases excessively, the energy density of the all-solid-state secondary battery decreases and the internal resistance of the all-solid-state secondary battery due to the negative electrode active material layer (25, 25') increases, making it difficult to improve the lifespan characteristics of the all-solid-state secondary battery.

[0109] If the thickness of the negative electrode active material layer (25, 25') decreases, for example, the charge capacity of the negative electrode active material layer (25, 25') also decreases. The charge capacity of the negative electrode active material layer (25, 25') is, for example, 50% or less, 40% or less, 30% or less, 20% or less, 10% or less, 5% or less, or 2% or less compared to the charge capacity of the positive electrode active material layer (22, 22'). The charge capacity of the negative electrode active material layer (25, 25') is, for example, 0.1% to 50%, 0.1% to 40%, 0.1% to 30%, 0.1% to 20%, 0.1% to 10%, 0.1% to 5%, or 0.1% to 2% compared to the charge capacity of the positive electrode active material layer (22, 22'). If the charge capacity of the negative electrode active material layer (25, 25') is excessively small, the thickness of the negative electrode active material layer (25, 25') becomes very thin, and thus, during repeated charge and discharge processes, lithium dendrites formed between the negative electrode active material layer (25, 25') and the negative electrode current collector (24, 24') cause the negative electrode active material layer (25, 25') to collapse, making it difficult to improve the lifespan characteristics of the all-solid-state secondary battery. If the charge capacity of the negative electrode active material layer (25, 25') increases excessively, the energy density of the all-solid-state secondary battery decreases, and the internal resistance of the all-solid-state secondary battery caused by the negative electrode active material layer (25, 25') increases, making it difficult to improve the lifespan characteristics of the all-solid-state secondary battery.

[0110] The charge capacity of the positive active material layer (22, 22') is obtained by multiplying the charge capacity density (mAh / g) of the positive active material by the mass of the positive active material in the positive active material layer (22, 22'). When multiple types of positive active materials are used, the charge capacity density × mass value is calculated for each positive active material, and the sum of these values ​​is the charge capacity of the positive active material layer (22, 22'). The charge capacity of the negative active material layer (25, 25') is calculated in the same way. That is, the charge capacity of the negative active material layer (25, 25') is obtained by multiplying the charge capacity density (mAh / g) of the negative active material by the mass of the negative active material in the negative active material layer (25, 25'). When multiple types of negative active materials are used, the charge capacity density × mass value is calculated for each negative active material, and the sum of these values ​​is the capacity of the negative active material layer (25, 25'). Here, the charge capacity density of the positive and negative active materials is the capacity estimated using an all-solid-state half-cell using lithium metal as the counter electrode. The charge capacity of the positive active material layer (22, 22') and the negative active material layer (25, 25') is directly measured by measuring the charge capacity using an all-solid-state half-cell. By dividing the measured charge capacity by the mass of each active material, the charge capacity density is obtained. Alternatively, the charge capacity of the positive active material layer (22, 22') and the negative active material layer (25, 25') may be the initial charge capacity measured during the first cycle of charging.

[0111] The negative electrode current collector (24, 24') is composed of a material that does not react with, for example, lithium, that is, does not form either an alloy or a compound. The material constituting the negative electrode current collector (24, 24') may be, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), and nickel (Ni), but is not necessarily limited to these; any material used as an electrode current collector in the relevant technical field is acceptable. The negative electrode current collector (24, 24') may be composed of one of the metals described above, or may be composed of an alloy or coating material of two or more metals. The negative electrode current collector (24, 24') is, for example, in the form of a plate or a foil.

[0112] [All-solid-state secondary battery]

[0113] The all-solid-state secondary battery includes the aforementioned electrode structure (10, 30).

[0114] FIG. 4 is a schematic diagram of an all-solid-state secondary battery according to one embodiment.

[0115] Referring to FIG. 4, the all-solid-state secondary battery is in the form of a stack. The all-solid-state secondary battery (40) has a positive electrode layer (36, 36') in which a positive electrode active material layer (32, 32') is disposed on the upper and lower surfaces of a positive electrode current collector (31), a solid electrolyte layer (33, 33') is disposed on one side of the positive electrode layer (36, 36'), and a negative electrode layer (37, 37') composed of a negative electrode active material layer (34, 34') and a negative electrode current collector (35, 35') is disposed on one side of the solid electrolyte layer (33, 33'). Insulating layers (38, 38') are disposed on both sides of the positive electrode layer (36, 36'), the solid electrolyte layer (33, 33'), and the negative electrode layer (37, 37'), respectively. A support member (39, 39') is positioned on one side of the above negative current collector (35, 35'). The all-solid-state secondary battery (40) is manufactured by applying a warm isostactic press (WIP) to the upper and lower support members (39, 39') to form positive and negative terminals, respectively.

[0116] In a solid-state secondary battery (40), insulating layers (38, 38') are disposed on both sides of a positive electrode layer (36, 36'), a solid electrolyte layer (33, 33'), and a negative electrode layer (37, 37'), thereby suppressing short circuits and improving lifespan characteristics while minimizing the reduction in initial capacity.

[0117] The creative idea is explained in more detail through the following examples and comparative examples. However, the examples are intended to illustrate the creative idea and do not limit the scope of the creative idea to these examples alone.

[0118] [Example]

[0119] Example 1: PVdF + Al 2 O 3 All-solid-state secondary battery with insulating layer

[0120] (Cathode layer manufacturing)

[0121] A SUS foil with a thickness of 10 μm was prepared as a negative electrode current collector. In addition, carbon black (CB) with a primary average particle size (D50) of about 35 nm and silver (Ag) particles with an average diameter (D50) of about 60 nm were prepared as negative electrode active materials.

[0122] 4g of a mixed powder, prepared by mixing carbon black (CB) and silver (Ag) particles in a weight ratio of 3:1, was placed in a container, and 4g of an NMP solution containing 7 wt% of PVDF binder (Kureha # 9300) was added to prepare a mixed solution. Subsequently, a slurry was prepared by stirring the mixed solution while gradually adding NMP. The prepared slurry was applied to a SUS sheet using a doctor blade and dried in air at 60°C for 20 minutes. The resulting laminate was vacuum dried at 100°C for 12 hours to fabricate a cathode layer. The thickness of the cathode active material layer of the Ag-C nanocomposite contained in the cathode layer was approximately 7 μm. The volume ratio of Ag in the above Ag-C nanocomposite was approximately 8 volume%, and the Ag content used during battery manufacturing was approximately 12 mg / Ah.

[0123] (Anode layer manufacturing)

[0124] LiNi coated with Li2O-ZrO2 (LZO) as a cathode active material 0.8 Co 0.15 Mn 0.05O2 (NCM) was prepared. An LZO-coated cathode active material was prepared according to the method disclosed in Korean Patent Publication No. 10-2016-0064942. As a solid electrolyte, Li6PS5Cl (D50 = 0.5 μm, crystalline), which is an argyrodite-type crystal, was prepared. As a binder, a polytetrafluoroethylene (PTFE) binder (Teflon binder from DuPont) was prepared. As a conductive agent, carbon nanofiber (CNF) was prepared. A mixture of these materials and xylene solvent was mixed in a weight ratio of cathode active material: solid electrolyte: conductive agent: binder = 85:15:3:1.5, formed into a sheet, and then vacuum dried at 40°C for 8 hours to produce a cathode sheet. The cathode sheet was pressed onto one side of a cathode current collector made of carbon-coated aluminum foil with a thickness of 18 μm to produce a cathode layer. The thickness of the anode layer was approximately 105 μm. The loading level of the anode layer was approximately 6.8 mAh / cm² 2 It was.

[0125] (Preparation of solid electrolyte layer)

[0126] A mixture was prepared by adding 1 part by weight of an acrylic binder to 99 parts by weight of a solid electrolyte, specifically an argyrodite-type crystal Li6PS5Cl (D50 = 3.0 μm, crystalline). Xylene (FUJIFILM Wako Pure Chemical Corporation) and isobutyl isobutyrate (Aldrich) were added to the prepared mixture in a 50:50 weight ratio, and a slurry was prepared by stirring at 2000 rpm for 6 minutes using a planetary centrifugal mixer (AR-100). The prepared slurry was applied onto a 75 μm thick polyethylene terephthalate film using a doctor blade, and a laminate was obtained by drying on a hot plate at 50 °C for several minutes. The obtained laminate was vacuum dried at 40 °C for 8 hours. A solid electrolyte layer was prepared by the above process. The thickness of the solid electrolyte layer was about 40 μm, and it was reduced to about 30 μm by applying pressure in the battery.

[0127] (Preparation of slurry for forming an insulating layer)

[0128] 40 g of mixed powder, prepared by adding and mixing PVdF powder (Kureha # 9300) and Al2O3 powder (50 nm, manufactured by Sigma Aldrich) in a weight ratio of 1:3, was placed in a container, and an acetone solvent was added to prepare a mixed solution. Subsequently, a slurry for forming an insulating layer was prepared by stirring the mixed solution while adding the acetone solvent little by little.

[0129] (Manufacturing of all-solid-state secondary batteries)

[0130] As shown in FIG. 3, a solid electrolyte layer (33) was arranged so that a negative electrode active material layer (34) contacted the solid electrolyte layer (33) on the negative electrode layer (37), and an anode layer (36) was arranged on the solid electrolyte layer (33) to manufacture a laminate. The margin of the width of the solid electrolyte layer (33) was about 2%.

[0131] The above-described slurry for forming an insulating layer was applied integrally to both sides of a laminate composed of the cathode layer (37), the anode layer (36), and the solid electrolyte layer (33) using a doctor blade, and dried in air to produce an electrode structure having an insulating layer (38). The storage modulus (E') of the insulating layer (38) was 6.471 GPa, and the loss tangent (tanδ) was 0.045.

[0132] An electrode structure having insulating layers (38) on both sides was placed in a laminate bag and vacuum sealed. Subsequently, the vacuum-sealed electrode structure was pressed by a warm isostactic press (WIP) at a pressure of 500 MPa. Afterward, the electrode structure was removed from the laminate bag, and the Al and Ni terminals of the positive and negative electrodes were welded using an ultrasonic welder. Subsequently, the electrode structure with the protruding Al and Ni terminals was placed in a laminate bag and vacuum sealed again to manufacture an all-solid-state secondary battery (40).

[0133] Example 2: Cellulose + Glass Fiber + Al(OH) 3 All-solid-state secondary battery with insulating layer

[0134] In the preparation of a slurry for forming an insulating layer, 30 g of mixed powder was prepared by adding and mixing nanocellulose (art clay, manufactured by Pinocchio Co., Ltd.), glass fiber (diameter = 2.7 μm, manufactured by Whatman), and Al(OH)3 powder (5 μm, manufactured by Sigma Aldrich) in a weight ratio of 1:1:1, placing the mixture in a container, adding purified water, and grinding it to prepare a slurry for forming an insulating layer. Then, the slurry for forming an insulating layer was dried at 100°C for 12 hours to form a sheet-shaped insulating layer, and the insulating layer was perforated in a '□' shape to have an inner diameter equal to that of the solid electrolyte layer (33) of the laminate composed of the negative electrode layer (37), the positive electrode layer (36), and the solid electrolyte layer (33), and arranged to wrap around the four sides of the laminate without separate adhesion, except that an all-solid-state secondary battery (40) was prepared in the same manner as in Example 1. The storage elastic modulus (E') of the insulating layer (38) was 19.87 GPa, and the loss tangent (tanδ) was 0.024.

[0135] Example 3: All-solid-state secondary battery having an insulating layer with a three-layer structure of cellulose + epoxy resin + cellulose

[0136] An all-solid-state secondary battery (40) was manufactured in the same manner as in Example 1, except that instead of preparing a slurry for forming an insulating layer, 2 g of epoxy adhesive (EP935, manufactured by Ogong Co., Ltd.) was applied between two sheets of cellulose paper with a thickness of 60 μm to prepare a three-layer insulating layer structure in which cellulose, epoxy resin, and cellulose are sequentially arranged, and the laminate composed of the negative electrode layer (37), the positive electrode layer (36), and the solid electrolyte layer (33) was fixed to both sides using the epoxy adhesive. The storage elastic modulus (E') of the insulating layer (38) was 39.63 GPa, and the loss tangent (tanδ) was 0.034.

[0137] Comparative Example 1: PP + ZrO 2 All-solid-state secondary battery with insulating layer

[0138] A polypropylene zirconia film with a thickness of approximately 230 μm (MKP1848C capacitor material (semi-finished product), manufactured by Vishay) was prepared instead of preparing a slurry for forming an insulating layer, and a '□' shaped perforation was made to have an inner diameter equal to that of the solid electrolyte layer (33) of the laminate composed of the cathode layer (37), the anode layer (36), and the solid electrolyte layer (33), and the film was arranged to wrap around the four sides of the laminate without separate adhesive, except that the film was arranged in the same manner as in Example 1. The storage modulus (E') of the insulating layer (38) was 1.491 GPa, and the loss tangent (tanδ) was 0.098.

[0139] Comparative Example 2: All-solid-state secondary battery with PMMA insulating layer

[0140] An all-solid-state secondary battery (40) was manufactured in the same manner as in Example 1, except that instead of preparing a slurry for forming an insulating layer, a transparent polymethyl methacrylate (PMMA) film (manufactured by Sumitomo) with a thickness of 350 μm was prepared, and the film was perforated in a '□' shape to have an inner diameter equal to that of the solid electrolyte layer (33) of the laminate composed of the cathode layer (37), the anode layer (36), and the solid electrolyte layer (33), and arranged to wrap around the four sides of the laminate without separate adhesion. The storage elastic modulus (E') of the insulating layer (38) was 2.520 GPa, and the loss tangent (tanδ) was 0.157.

[0141] Comparative Example 3: All-solid-state secondary battery with a PTFE insulating layer

[0142] An all-solid-state secondary battery (40) was manufactured in the same manner as in Example 1, except that instead of preparing a slurry for forming an insulating layer, a polytetrafluoroethylene (PTFE) film (Hypersheet, manufactured by Goretech) with a thickness of 300 μm was prepared, and it was perforated in a '□' shape to have an inner diameter equal to that of the solid electrolyte layer (33) of the laminate composed of the cathode layer (37), the anode layer (36), and the solid electrolyte layer (33), and arranged to wrap around the four sides of the laminate without separate adhesion. The storage elastic modulus (E') of the insulating layer (38) was 0.200 GPa, and the loss tangent (tanδ) was 0.198.

[0143] The materials constituting the insulating layer of the all-solid-state secondary battery (40) manufactured according to Examples 1 to 3 and Comparative Examples 1 to 3, and the storage elastic modulus (E'), storage inelastic modulus (E"), and loss tangent (loss tangent, tanδ, E" / E') of these materials are summarized and shown in Table 1 below. The storage elastic modulus (E') and storage inelastic modulus (E") of the insulating layer materials were derived by dynamic mechanical analysis (DMA) using a sinusoidal wave shape of 1 Hz frequency on a sample of 10 mm x 5 mm size.

[0144] Insulating layer material Storage modulus [E', GPa] Storage inelastic modulus [E", GPa] Loss tangent[tanδ, E" / E'] Example 1 PVdF + Al2O3 6.471 0.29 0.045 Example 2 Cellulose + Glass fiber + Al(OH)3 19.87 0.47 0.024 Example 3 Cellulose + Epoxy Resin + Cellulose 3-layer structure 39.63 1.349 0.034 Comparative Example 1 PP + ZrO2 1.491 0.146 0.098 Comparative Example 2 PMMA 2.520 0.392 0.157 Comparative Example 3 PTFE 0.200 0.039 0.198

[0145] Evaluation Example 1: Charge / Discharge Test

[0146] The charge-discharge characteristics of the all-solid-state secondary batteries prepared according to Examples 1 to 3 and Comparative Examples 1 to 3 were evaluated by the following charge-discharge test. The charge-discharge test was performed by placing the all-solid-state secondary batteries in a constant temperature bath at 45°C.

[0147] The first cycle involved charging with a constant current of 0.1 C until the battery voltage reached 4.25 V, then switching to constant voltage charging when it reached 4.25 V and charging until the charging current reached 0.05 C. Subsequently, discharging was performed with a constant current of 0.1 C until the battery voltage reached 2.5 V.

[0148] Subsequently, the first cycle was repeated to perform charge and discharge cycles up to 50 cycles, and the capacity retention rate was calculated according to Equation 1 below. The results of the initial capacity and capacity retention rate are shown in Table 2 and Figure 4 below. The initial capacity is the discharge capacity in the first cycle.

[0149] [Equation 1]

[0150] Capacity Retention Rate (%) = [ ] x 100

[0151] Initial capacity [mAh / g] Capacity retention rate[%] Example 1 188.44 92.7 Example 2 190.03 92.8 Example 3 189.86 93.2 Comparative Example 1 188.22 77.6 Comparative Example 2 188.98 38.6 Comparative Example 3 156.86 Short circuit occurrence (1st cycle)

[0152] As shown in Table 1 and Figure 4 above, the all-solid-state secondary batteries prepared according to Examples 1 to 3 had an initial capacity that was equivalent to or improved compared to the all-solid-state secondary batteries prepared according to Comparative Examples 1 to 3, and the capacity retention rate was also improved.

[0153] From this, it can be seen that the all-solid-state secondary battery manufactured according to Examples 1 to 3 includes an insulating layer having a storage elastic modulus of 6.471 GPa or more and a loss tangent of less than 0.045 on both sides of the electrode structure, thereby preventing initial short circuits and having a restoring force during charging and discharging, resulting in excellent initial capacity and capacity retention rate. Explanation of the symbols

[0154] 1, 26, 26', 36, 36': Anode layer, 2, 23, 23', 33, 33': Solid electrolyte layer, 3, 27, 27', 37, 37': Cathode layer, 4, 28, 28', 38, 38': Insulating layer, 10, 30: Electrode structure 21, 31: Positive current collector, 22, 22', 32, 32': Positive active material layer, 24, 24', 35, 35': Negative current collector, 25, 25', 34, 34': Cathode active material layer, 39, 39': Support member, 40: All-solid-state secondary battery, w: Margin width

Claims

Claim 1 An electrode structure comprising an anode layer, a cathode layer, and a solid electrolyte layer disposed between the anode layer and the cathode layer, wherein the anode layer comprises an anode current collector and an anode active material layer disposed on at least one surface of the anode current collector, the cathode layer comprises a cathode current collector and a cathode active material layer disposed on at least one surface of the cathode current collector, and an insulating layer having a storage modulus (E') of greater than 4.0 GPa on both sides integrally surrounding the anode layer, the cathode layer, and the solid electrolyte layer, the insulating layer comprises a polymer, or a composite of a polymer and an inorganic material, wherein the polymer comprises a fluorine-based polymer, a cellulose-based polymer, an epoxy-based resin, or a combination thereof, and the inorganic material comprises aluminum oxide or aluminum hydroxide. Electrode structure. Claim 2 An electrode structure according to claim 1, wherein the insulating layer has a loss tangent (tanδ) of less than 0.

5. Claim 3 In claim 1, the insulating layer is 1 x 10 6 Electrode structure having a resistivity of ohm / cm or greater. Claim 4 An electrode structure according to claim 1, wherein the insulating layer is at least one layer. Claim 5 delete Claim 6 delete Claim 7 An electrode structure according to claim 1, wherein the volume ratio of the polymer in the composite of the polymer and the inorganic material is 50 volume% or more based on 100 volume% of the total composition for forming the composite. Claim 8 delete Claim 9 An electrode structure according to claim 1, wherein the composite density of the positive active material layer is 3.0 g / cc or higher. Claim 10 An electrode structure according to claim 1, wherein the positive active material layer comprises a sulfide-based solid electrolyte. Claim 11 An electrode structure according to claim 1, wherein the negative electrode active material layer comprises one or more selected from a carbon-based negative electrode active material and a metal or metal-metal negative electrode active material. Claim 12 In claim 11, the electrode structure wherein the carbon-based negative electrode active material comprises one or more selected from amorphous carbon and crystalline carbon. Claim 13 An electrode structure according to claim 11, wherein the metal or metalloid cathode active material comprises one or more selected from the group consisting of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn). Claim 14 An electrode structure according to claim 1, wherein the solid electrolyte layer does not have a margin at both ends in the width direction or has a margin of 2% or less of the width of the solid electrolyte layer. Claim 15 The electrode structure according to claim 1, wherein the solid electrolyte layer comprises a sulfide-based solid electrolyte represented by the following chemical formula 1: [Chemical Formula 1]Li + 12-n-x A n+ X 2- 6-x Y - x In the above formula, A is P, As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, or Ta, X is S, Se, or Te, Y is Cl, Br, I, F, CN, OCN, SCN, or N3, and 1 < n < 5, 0 < x < 2. Claim 16 The electrode structure according to claim 1, wherein the solid electrolyte layer has a peel strength of 0.2 gf / mm or more with respect to the anode layer or the cathode layer. Claim 17 In claim 1, the electrode structure is in the form of a jelly roll or a stack. Claim 18 An electrode structure according to claim 1, wherein cracks do not occur in the electrode structure when the electrode structure is compressed to 20-30% of its thickness in the thickness direction. Claim 19 An all-solid-state secondary battery comprising an electrode structure described in any one of claims 1 to 4, 7, and 9 to 18.

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